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Duo Protection for Slack

Duo offers a variety of methods for adding two-factor authentication and flexible security policies to Slack SSO logins, complete with inline self-service enrollment and Duo Prompt.

Overview

As business applications move from on-premises to cloud hosted solutions, users experience password fatigue due to disparate logons for different applications. Single sign-on (SSO) technologies seek to unify identities across systems and reduce the number of different credentials a user has to remember or input to gain access to resources.

While SSO is convenient for users, it presents new security challenges. If a user's primary password is compromised, attackers may be able to gain access to multiple resources. In addition, as sensitive information makes its way to cloud-hosted services it is even more important to secure access by implementing two-factor authentication.

Duo Access Gateway

Duo Access Gateway (DAG), our on-premises SSO product, layers Duo's strong authentication and flexible policy engine on top of Slack logins using the Security Assertion Markup Language (SAML) 2.0 authentication standard. Duo Access Gateway authenticates your users using existing on-premises or cloud-based directory credentials and prompts for two-factor authentication before permitting access to Slack.

Duo Access Gateway is included in the Duo Beyond, Duo Access, and Duo MFA plans, which also include the ability to define policies that enforce unique controls for each individual SSO application. For example, you can require that Salesforce users complete two-factor authentication at every login, but only once every seven days when accessing Slack. Duo checks the user, device, and network against an application's policy before allowing access to the application.

Deploy Duo Access Gateway

  1. Install Duo Access Gateway on a server in your DMZ. Follow our instructions for deploying the server, configuring DAG settings, and adding your primary authentication source.

  2. Add the attributes from the table below that correspond to the Duo attributes Mail attribute, Last name attribute, and First name attribute in the "Attributes" field when configuring your Active Directory or OpenLDAP authentication source in the DAG admin console, separated by a comma. For example, if Active Directory is your authentication source, enter mail,sn,givenName in the "Attributes" field.

    Duo Attribute Active Directory OpenLDAP
    Mail attribute mail mail
    First name attribute givenName gn
    Last name attribute sn sn

    If your organization uses other directory attributes than the ones listed here then enter those attribute names instead. If you've already configured the attributes list for another cloud service provider, append the additional attributes not already present to the list, separated by a comma.

  3. After completing the initial DAG configuration steps, click Applications on the left side of the Duo Access Gateway admin console.

  4. Scroll down the Applications page to the Metadata section. This is the information you need to provide to Slack when configuring SSO. Click the Download Certificate link to obtain the token signing certificate (the downloaded file is named "dag.crt").

    DAG Metadata Information

Create the Slack Application in Duo

  1. Log on to the Duo Admin Panel and navigate to Applications.

  2. Click Protect an Application, locate SAML - Slack in the applications list, and click Protect this Application. See Getting Started for help.

  3. The Team name is the subdomain used when logging into your company's Slack site. For example, if your Slack team login URL is https://teamname.slack.com, enter teamname.

  4. Slack uses the Mail attribute, First name attribute, and Last name attribute when authenticating. We've mapped those to DAG supported authentication source attributes as follows:

    Duo Attribute Active Directory OpenLDAP SAML IdP Google Azure
    Mail attribute mail mail mail email mail
    First name attribute givenName gn givenName given_name givenName
    Last name attribute sn sn sn family_name surname

    If you are using non-standard attributes for your authentication source, check the Custom attributes box and enter the names of the attributes you wish to use instead.

  5. Click Save Configuration to generate a downloadable configuration file.

    Duo Slack Application Settings

  6. You can adjust additional settings for your new SAML application at this time — like changing the application's name from the default value, enabling self-service, or assigning a group policy — or come back and change the application's policies and settings after you finish SSO setup. If you do update any settings, click the Save Changes button when done.

  7. Click the Download your configuration file link to obtain the Slack application settings (as a JSON file).

    Important: This file contains information that uniquely identifies this application to Duo. Secure this file as you would any other sensitive or password information. Don't share it with unauthorized individuals or email it to anyone under any circumstances!

Add the Slack Application to Duo Access Gateway

  1. Return to the Applications page of the DAG admin console session.

  2. Click the Choose File button in the "Add Application" section of the page and locate the Slack SAML application JSON file you downloaded from the Duo Admin Panel earlier. Click the Upload button after selecting the JSON configuration file.

  3. The Slack SAML application is added.

    Slack Application Added

Enable Slack SSO

Add the Duo Access Gateway as a new single sign-on provider for Slack.

  1. Log on your Slack team site as an administrator. On the sidebar menu navigate to AdministrationAuthentication. Click the Configure link for "SAML authentication".

  2. On the "Choose your SAML provider" page, select Custom SAML 2.0 and click Configure.

  3. Copy the SSO URL information from the Duo Access Gateway admin console Metadata display and paste it into the Slack SAML 2.0 Endpoint (HTTP) field.

    Example: https://yourserver.example.com/dag/saml2/idp/SSOService.php

  4. Copy the Entity ID information from the Duo Access Gateway admin console Metadata display and paste it into Slack's Identity Provider Issuer field.

    Example: https://yourserver.example.com/dag/saml2/idp/metadata.php

  5. The "Public Certificate" is the text of the DAG Metadata certificate supplied by Duo Access Gateway. Open the dag.crt file in a text editor (like Notepad), and copy the entire contents of the file (including the -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- lines). Paste the certificate file text into this field.

    Slack Single Sign-On Setting Edit

  6. Click Expand next to "Advanced Options". New options will appear.

  7. Next to Service Provider Issuer type https://slack.com/

    Slack Issuer Setting

  8. Select which team members must use SSO authentication and configure other options under "Settings".

  9. After you've entered all the required information click Save Configuration and Send Binding Emails. This automatically redirects you to the Duo Access Gateway to bind your Slack account to your SSO account. This action also sends an email to your Slack team users with the unique links used to bind their Slack accounts with their SSO accounts.

    See the Slack Help Center for more information about SSO binding emails.

    Slack Single Sign-On Additional Setting

  10. Successful completion of your Slack and SSO account binding redirects you back to the Slack Team Settings page.

Learn more about Slack SSO at the Slack Help Center.

Using SSO

You can log on to Slack using your team login page e.g. https://teamname.slack.com. Clicking the Sign in with SAML button redirects you to the Duo Access Gateway login page. Enter your primary directory logon information, approve Duo two-factor authentication, and get redirected back to the Slack site after authenticating.

DAG Login and Authentication Prompt

Congratulations! Your Slack users now authenticate using Duo Access Gateway.

Microsoft AD FS

Microsoft's Active Directory Federation Services (AD FS) is a popular choice for SSO because it easily integrates with the AD identity store many organizations already have deployed. Duo's support for cloud applications and SSO drops in to an existing AD FS installation to provide secondary authentication after a user passes primary authentication (successful Active Directory logon).

If you don't already have AD federation running the first step is to install and configure Microsoft AD FS in your organization. Microsoft's Deployment Guides for AD FS versions 2.0, 2.1, and 3.0 are available on the TechNet site.

Once your AD FS services are up and running, the second step is to configure the SSO partnership between your AD FS service and the external cloud resource, in this case Slack. Learn more about configuring Slack SSO with AD FS at the Slack Help Center.

After you have successfully configured and tested AD FS SSO login to Slack using your AD domain credentials, you can then install the Duo AD FS integration. AD FS protection is included with Duo's paid plans.

With the Duo integration for AD FS installed, users pass primary authentication to the AD FS service as usual. Once primary authentication succeeds, users are forwarded to the Duo service for secondary authentication. After approving logon using one of Duo's authentication methods, the user is fully logged in to Slack.

Other Identity Partners

Using a third-party SSO provider for cloud application access? Duo partners with leading cloud SSO providers like Okta and OneLogin to secure access with our strong and flexible authentication platform.

You can also use Duo two-factor authentication with CAS and Shibboleth on-premises IdPs.

Troubleshooting

Need some help? Try searching our Knowledge Base articles or Community discussions. For further assistance, contact Support.

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